System and method for predicting negative pressure of brake booster of vehicle

ABSTRACT

A system for predicting a negative pressure of a brake booster of a vehicle includes: a driving information detector detecting driving information related to driving of the vehicle; and a controller determining a negative pressure of an intake manifold based on a pressure of the intake manifold and an atmospheric pressure which is the driving information and including a booster negative pressure predictor predicting the negative pressure of the brake booster by integrating over time a change rate according to a charging rate and a discharging rate of the negative pressure determined using a negative pressure of the brake booster determined in a previous cycle according to a logic for predicting the negative pressure of the brake booster and the negative pressure of the intake manifold of a current cycle and an imitated brake pedal force signal of the current cycle imitating an acceleration of the vehicle.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2019-0178317 filed on Dec. 30, 2019, and Korean Patent ApplicationNo. 10-2020-0050755 filed on Apr. 27, 2020, the entire contents of whichis incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a brake booster negative pressureprediction system and a method thereof, and more particularly, to asystem and a method for predicting a negative pressure of a brakebooster of a vehicle capable of improving cooling performance andbraking performance of the vehicle in which a brake booster sensor and abrake pedal force sensor are omitted.

Description of Related Art

In general, when a brake negative pressure stored in a brake booster ofa vehicle is insufficient, a brake pedal of the vehicle is hardened sothat a risk of an accident increases. To improve the present problem, alogic to recover the brake negative pressure by stopping an operation ofvarious auxiliary devices such as an air conditioner (A/C) is applied ina situation where the brake negative pressure is insufficient.

A compressor included in the air conditioner affects an engine load ofthe vehicle because the compressor utilizes a power of an engine of thevehicle. When the brake negative pressure falls below a certain value,an operation of the air conditioner is stopped or cut to secure adriving power required for the brake negative pressure.

The brake negative pressure is a pressure stored in an actual brakebooster and an actual measured value measured using a real boostersensor. However, to perform the control for stopping an operation of theair conditioner, many manufacturers use a negative pressure of an intakemanifold of the vehicle, which generates a negative pressure of thebrake booster, instead of using the real booster sensor due to problemssuch as cost increase. The negative pressure of the intake manifoldmeans a difference between an atmospheric pressure and a pressure of theintake manifold.

However, in the case of using the intake manifold negative pressure ofthe intake manifold, an operation of the air conditioner is frequentlystopped because the negative pressure of the intake manifold isdetermined less even when sufficient pressure is stored in the brakebooster.

When a vehicle that does not have the booster sensor raises a referencepressure for the control for stopping an operation of the airconditioner using the negative pressure of the intake manifold, there isa problem that cooling performance deteriorates due to frequent stop ofthe air conditioner. When the reference pressure is lowered, a frequencyof stop of the air conditioner is decreased, but braking performancedeteriorates.

Therefore, the control for stopping the operation of the air conditionerusing the negative pressure of the intake manifold needs to becorrected.

The information included in the present Background of the Inventionsection is only for enhancement of understanding of the generalbackground of the invention and may not be taken as an acknowledgementor any form of suggestion that the present information forms the priorart already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing asystem and a method for predicting a negative pressure of a brakebooster of a vehicle configured for improving cooling performance andbraking performance of the vehicle through a logic for predicting anegative pressure of a brake booster that utilizes a charging rate and adischarging rate of the negative pressure generated based on a negativepressure of an intake manifold and an imitated pedal force signal brakeof the vehicle which does not include a brake booster sensor and a brakepedal force sensor.

An exemplary embodiment of the present invention may provide the systemfor predicting the negative pressure of the brake booster of thevehicle, including: a driving information detector configured to detectdriving information related to the vehicle according to driving of thevehicle; and a controller engaged to the driving information detectorand configured to determine a negative pressure of an intake manifoldbased on a pressure of the intake manifold and an atmospheric pressurewhich is the driving information and including a booster negativepressure predictor configured to predict the negative pressure of thebrake booster by integrating over time a change rate according to acharging rate and a discharging rate of the negative pressure determinedusing a negative pressure of the brake booster determined in a previouscycle according to a logic for predicting the negative pressure of thebrake booster and the negative pressure of the intake manifold of acurrent cycle and an imitated brake pedal force signal of the currentcycle imitating an acceleration of the vehicle.

The controller may be configured to generate an acceleration inflectionrecognition signal by crossing the imitated brake pedal force signalover time and a reference line which is a zero crossing.

The controller may be configured to correct the charging rate and thedischarge rate based on the acceleration inflection recognition signal.

When a predicted negative pressure of the brake booster is less than orequal to a reference negative pressure of a control for stopping anoperation of an air conditioner of the vehicle, the controller may beconfigured to determine that the predicted negative pressure of thebrake booster is insufficient to stop the operation of the airconditioner.

The driving information detector may be configured to detect the drivinginformation from at least one of a vehicle speed sensor, a vehicleacceleration sensor, a speed stage sensor, an accelerator pedal sensor,a brake pedal operation sensor, a timer, and an atmospheric pressuresensor.

The booster negative pressure predictor may be configured to collect thenegative pressure of the intake manifold and the driving information andto generate the negative pressure of the brake booster predicted in acycle of a time period.

The booster negative pressure predictor may include: a charging modelmodule configured to determine a first differential pressure over timeusing the negative pressure of the brake booster determined in theprevious cycle and the negative pressure of the intake manifold of thecurrent cycle; a discharging model module configured to take adifference between the negative pressure of the brake booster determinedin the previous cycle and the negative pressure of the intake manifoldof the current cycle as a basic factor, and to compensate for the basicfactor using the imitated brake pedal force signal to determine a seconddifferential pressure over time; a summing module configured todetermine a change rate by adding a discharging rate of the negativepressure of the brake booster corresponding to the second differentialpressure to a charging rate of the negative pressure of the brakebooster corresponding to the first differential pressure; and anintegration module configured to integrate the change rate over time andto output the predicted negative pressure of the brake booster.

The charging rate of the negative pressure of the brake boosteraccording to the first differential pressure may be output as a positivevalue, and the discharging rate of the negative pressure of the brakebooster according to the second differential pressure may be output as anegative value.

The charging model module may be configured to determine the chargingrate using a control map using the first differential pressure as aninput value thereof.

The discharging model module may be configured to determine amultiplication factor for correcting the discharging rate using acorrection map using a displacement change amount of the imitated brakepedal force as an input value thereof.

The discharging model module may be configured to use an additionalcorrection amount according to a repetition frequency of a zero crossinggenerated when repeated braking due to an on state and an off state of abrake operation signal continuously occurs to increase the dischargingrate.

The discharging model module may be configured to use an additionalcorrection amount to increase the discharging rate when the dischargingmodel module continuously detects that the acceleration of the vehicleor a speed of the vehicle has an amplitude greater than or equal to areference amplitude.

The integration module may be configured to feedback the predictednegative pressure of the brake booster to the charging model module andthe discharging model module so that the predicted negative pressure isused to determine a charging rate and a discharging rate of a next cyclegenerated after the current cycle.

The controller may be configured to restart the vehicle in a state inwhich a start of the vehicle is stopped by an idle stop and go (ISG)system when the predicted negative pressure of the brake booster is lessthan or equal to a reference negative pressure.

An exemplary embodiment of the present invention may provide the methodfor predicting the negative pressure of the brake booster of thevehicle, including: a) collecting, by a controller, driving informationrelated to the vehicle according to driving of the vehicle to determinean imitated brake pedal force signal imitating change of an accelerationof the vehicle and a negative pressure of an intake manifold; b)determining, by the controller, a first differential pressure over timeusing a negative pressure of the brake booster determined in a previouscycle and the negative pressure of the intake manifold of a currentcycle; c) taking, by the controller, a difference between the negativepressure of the brake booster determined in the previous cycle and thenegative pressure of the intake manifold of the current cycle as a basicfactor to determine a second differential pressure over time bycompensating for the basic factor using the imitated brake pedal forcesignal; and d) determining, by the controller, a change rate by adding adischarging rate of the negative pressure of the brake boostercorresponding to the second differential pressure to a charging rate ofthe negative pressure of the brake booster corresponding to the firstdifferential pressure to predict the negative pressure of the brakebooster by integrating the change rate over time.

Step a) may include: generating, by the controller, the imitated brakepedal force signal over time by filtering an acceleration change signalof the vehicle in an operation section of a brake of the vehicle; andgenerating, by the controller, an acceleration inflection recognitionsignal by crossing the imitated brake pedal force signal and a referenceline which is a zero crossing.

Step b) may include: setting, by the controller, an initial negativepressure of the brake booster generated when the previous cycle does notexist as a value less than the negative pressure of the intake manifold.

Step b) may include: determining, by the controller, the charging rateusing a control map using the first differential pressure as an inputvalue thereof.

Step c) may include: determining, by the controller, a multiplicationfactor for correcting the discharging rate using a correction map usinga displacement change amount of the imitated brake pedal force as aninput value thereof.

The method for predicting the negative pressure of the brake booster ofthe vehicle may further include: after step d), restarting, by thecontroller, the vehicle in a state in which a start of the vehicle isstopped by an idle stop and go (ISG) system when the predicted negativepressure of the brake booster is less than or equal to a referencenegative pressure.

The system and the method for predicting the negative pressure of thebrake booster of the vehicle according to the exemplary embodiment ofthe present invention may implement the logic for predicting thenegative pressure of the brake booster so that the exemplary embodimentof the present invention improves cooling performance and brakingperformance of the vehicle without cost increase due to addition ofhardware.

The exemplary embodiment of the present invention may determine thenegative pressure of the brake booster based on the charging rate andthe discharging rate modeled according to a change of the imitated brakeforce signal imitating a change in acceleration of the vehicle so thatthe exemplary embodiment of the present invention improves accuracy ofthe negative pressure of the brake booster to a level similar to a levelof an actual measured value of the brake booster sensor.

Furthermore, the exemplary embodiment of the present invention mayforcibly reduce a predicted value of the negative pressure of the brakebooster by detecting a repeated braking situation in which the brakeoperation signal is continuously changed and an acceleration signal ofthe vehicle is continuously changed more than or equal to a referenceamplitude so that the exemplary embodiment of the present inventionprevents a failure in which the predicted value exceeds the actualmeasured value.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph explaining prediction limit of a virtual brakenegative pressure.

FIG. 2 shows a configuration of a system for predicting a negativepressure of a brake booster of a vehicle according to various exemplaryembodiments of the present invention.

FIG. 3 is a graph illustrating a method of imitating a brake pedal forcesignal according to various exemplary embodiments of the presentinvention.

FIG. 4 illustrates an acceleration signal of a vehicle processed byimitating a phase of the brake pedal force signal according to variousexemplary embodiments of the present invention.

FIG. 5A, FIG. 5B, FIG. 6A, and FIG. 6B are graphs explaining a method ofprocessing acceleration of the vehicle according to various exemplaryembodiments of the present invention.

FIG. 7 is a block diagram showing a configuration of a booster negativepressure predictor according to various exemplary embodiments of thepresent invention.

FIG. 8 is a flowchart showing a method for predicting the negativepressure of the brake booster of the vehicle according to variousexemplary embodiments of the present invention.

FIG. 9 is a graph showing a result of predicting the negative pressureof the brake booster according to various exemplary embodiments of thepresent invention.

It may be understood that the appended drawings are not necessarily toscale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particularly intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the other hand, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

Exemplary embodiments of the present application will be described morefully hereinafter with reference to the accompanying drawings, in whichexemplary embodiments of the invention are shown. As those skilled inthe art would realize, the described embodiments may be modified invarious different ways, all without departing from the spirit or scopeof the present invention. Accordingly, the drawings and description areto be regarded as illustrative in nature and not restrictive. Likereference numerals designate like elements throughout the specification.

Throughout the specification, unless explicitly described to thecontrary, the word “comprise” and variations such as “comprises” or“comprising”, will be understood to imply the inclusion of statedelements but not the exclusion of any other elements. Furthermore, theterms “-er”, “-or” and “module” described in the specification meanunits for processing at least one function and operation and may beimplemented by hardware components or software components andcombinations thereof.

Throughout the specification, terms such as “first”, “second”, “A”, “B”,etc. may be used to describe various elements, but the elements may notbe limited by the terms. These terms are intended to distinguish oneelement from other elements, but the nature and the order or sequence ofthe elements is not limited by those terms.

Throughout the specification, a brake pedal force (or a brake pedaleffort) and a brake pedal pressure have a same meaning, and a pedalmeans a brake pedal unless otherwise stated.

Throughout the specification, a vehicle refers to a vehicle in which abrake booster sensor for measuring a negative pressure of the brakebooster and a brake pedal force sensor (or a brake pedal pressuresensor) for measuring a pressure of the brake pedal are not provided.

A system for predicting a negative pressure of a brake booster of thevehicle not having the brake pedal force sensor (or a device configuredfor predicting the negative pressure of the brake booster of thevehicle) and a method for predicting the negative pressure of the brakebooster of the vehicle according to various exemplary embodiments of thepresent invention will now be described in detail with reference to thedrawings.

A method of deriving a value of a virtual brake booster sensor forsolving a problem that occurs in a control for stopping an operation ofan air conditioner (A/C) of a vehicle using a negative pressure of anintake manifold of the vehicle will be referred to as follows.

The method may derive the virtual brake booster sensor value by modelinga change of the negative pressure of the brake booster according to thenegative pressure of the intake manifold of the vehicle and anacceleration of the vehicle so that the method reduces a frequency ofstop of the air conditioner.

However, since the method utilizes only the negative pressure of theintake manifold and the acceleration of the vehicle as basic factors forpredicting a brake negative pressure (or a pressure of the brakebooster), it is difficult to predict a change in the brake negativepressure due to a change of a brake pedal operation pattern of thevehicle when the vehicle decelerates with the acceleration.

FIG. 1 is a graph explaining prediction limit of the virtual brakenegative pressure.

Referring to FIG. 1 , to verify the method of deriving the virtual brakebooster sensor value (or a predicted value of the brake booster sensor),the virtual booster sensor value and an actual booster sensor valueaccording to a change in the brake pedal operation pattern of thevehicle are compared. The actual booster sensor value may be a measuredvalue of the brake booster sensor.

Conditions {circle around (1)}, {circle around (2)}, and {circle around(3)} of FIG. 1 represent different booster pressure changes according tothe change in the brake pedal operation pattern in a situation where thevehicle is decelerated with similar acceleration.

The condition {circle around (1)} shown as {circle around (1)} in FIG. 1is a case where the brake pedal of the vehicle is constantly pressedduring a single brake operation. The condition {circle around (2)} shownas {circle around (2)} in FIG. 1 is a case where a pressure of the brakepedal is frequently changed during a single brake operation. Thecondition {circle around (3)} shown as {circle around (3)} in FIG. 1 isa case where an on operation and an off operation of the brake pedal arerepeated. It is ideal that the virtual booster sensor value (or thepredicted value) is close to the actual booster sensor value (or themeasured value). A degree of similarity is defined as accuracy. A risksituation in which the predicted value exceeds or reverses the measuredvalue in a situation where the measured value is insufficient is definedas a failure. Considering safety of the vehicle, the accuracy has to behigh and the failure does not exist or has to be 0%.

In the case of the condition {circle around (1)}, the measured valuehardly decreases, but the predicted value determined based on thenegative pressure of the intake manifold and the acceleration rapidlydecreases. Thus, the accuracy deteriorates. In the case of the condition{circle around (2)}, the measured value and the predicted value issimilar. In the case of the condition {circle around (3)}, the predictedvalue exceeds the measured value so that the failure occurs.

To solve the above problem, the negative pressure of the brake boostermay be predicted using a charging rate and a discharging rate of thenegative pressure generated based on the negative pressure of the intakemanifold and a signal of the brake pedal force of the vehicle which doesnot include a brake booster sensor so that accuracy of prediction of thenegative pressure of the brake booster is improved. However, the aboveimprovement method may be applied to only a vehicle including the brakepedal force sensor outputting the brake pedal force signal.

Accordingly, the system and the method for predicting the negativepressure of the brake booster applicable to a vehicle without the brakebooster sensor and the brake pedal force sensor.

FIG. 2 shows a configuration of the system for predicting the negativepressure of the brake booster of the vehicle according to variousexemplary embodiments of the present invention.

Referring to FIG. 2 , the system for predicting the negative pressure ofthe brake booster of the vehicle 1 may be applied to the vehicle inwhich the brake booster sensor and the brake pedal force sensor isomitted, and may include a controller (e.g., an engine control unit(ECU)) 10 including a booster negative pressure predictor 100, a drivinginformation detector 20, and an air conditioning controller 30.

The controller 10 may determine a virtual negative pressure of the brakebooster according to a logic for predicting the negative pressure of thebrake booster, and may use driving information detected according to anoperation of the vehicle to perform a control for reducing a frequencyof stop of an air conditioner (A/C) of a vehicle using a predictednegative pressure of the brake booster.

The controller 10 may determine the negative pressure of the intakemanifold by subtracting a pressure of the intake manifold from anatmospheric pressure which is the driving information. The negativepressure of the intake manifold may be stored in the brake booster. Thecontroller 10 may derive a virtual brake booster sensor value bymodeling or predicting a change in a negative pressure of the brakebooster according to the negative pressure of the intake manifold of thevehicle and acceleration of the vehicle.

The controller 10 may include the booster negative pressure predictor100 that predicts a negative pressure of the brake booster similar to anactual measured value or a measured value based on the logic forpredicting the negative pressure of the brake booster. The boosternegative pressure predictor 100 may predict a current negative pressurek of the brake booster by integrating over time a change rate accordingto a charging rate and a discharging rate modeled (or determined) usinga negative pressure k−1 of the brake booster determined in a previouscycle according to the logic for predicting the negative pressure of thebrake booster and a negative pressure of the intake manifold of acurrent cycle and an imitated brake pedal force signal of the currentcycle imitating change of acceleration of the vehicle.

The system for predicting the negative pressure of the brake booster ofthe vehicle 1 may not directly measure a pedal force applied to thebrake pedal of the vehicle by a driver of the vehicle because the systemis applied to the vehicle in which the brake pedal force sensor isomitted.

Therefore, for the system for predicting the negative pressure of thebrake booster of the vehicle 1 to predict a reliable pedal force, amethod of indirectly predicting the pedal force is required. The methodof indirectly predicting the pedal force may be implemented by afunction or software of the controller 10.

The controller 10 may filter a change in acceleration of the vehicleover time to generate an acceleration inflection recognition signal thathas a tendency similar to the brake pedal force signal measured by thebrake pedal force sensor. In an exemplary embodiment of the presentinvention, since the acceleration inflection recognition signal issimilar to the brake pedal effort signal measured by the brake pedalforce sensor, the acceleration inflection recognition signal may bedefined as the imitated brake pedal force signal.

FIG. 3 is a graph illustrating a method of imitating the brake pedalforce signal according to various exemplary embodiments of the presentinvention.

Referring to FIG. 3 , the vehicle that does not include the brake pedalforce signal may filter an acceleration signal of the vehicle over timeto generate an acceleration processing signal such as {circle around(2)}. The acceleration processing signal may be similar to a change inan actual brake pedal force of the vehicle such as {circle around (1)}.The {circle around (1)} may represent a state in which the pedal forceis frequently changed under a single brake pedal operation. The {circlearound (2)} may be an imitated brake pedal force signal to imitate thechange in the actual brake pedal force.

When the acceleration processing signal such as {circle around (2)}crosses a predetermined reference line which is 0 (or a zero crossing),the acceleration inflection recognition signal such as {circle around(3)} may be generated. The zero crossing may be a reference point (e.g.,0) for determining a change of the acceleration processing signal usedwhen a discharging rate of the negative pressure of the brake booster iscorrected during prediction of the negative pressure of the brakebooster as shown in {circle around (4)}. The zero crossing may have anallowable error of ±0.01. When the acceleration inflection recognitionsignal is used, additional decompression of the predicted pressure ofthe brake booster may be performed.

The controller 10 may generate the imitated brake pedal force signal topredict the virtual negative pressure k of the brake booster as shown in{circle around (4)} through the booster negative pressure predictor 100.

FIG. 4 illustrates the acceleration signal of the vehicle processed byimitating a phase of the brake pedal force signal according to variousexemplary embodiments of the present invention.

FIG. 5A, FIG. 5B, FIG. 6A, and FIG. 6B are graphs explaining a method ofprocessing acceleration of the vehicle according to various exemplaryembodiments of the present invention.

Referring to FIG. 4 through FIG. 6 , when the driver presses the brakepedal to operate a brake of the vehicle while the vehicle is traveling,acceleration of the vehicle may change according to a degree ofapplication of the brake pedal force. When the brake pedal forceincreases, acceleration of the vehicle may decrease, and when the brakepedal force decreases, acceleration of the vehicle may increase. Thus, achange in acceleration of the vehicle and a change in the brake pedalforce may be correlated.

As shown in FIG. 5A, an acceleration signal of the vehicle shown in FIG.4 may has various combinations of frequencies according to a drivingstate of the vehicle. Since the acceleration signal has a lot ofinformation including the brake pedal force signal, it is difficult toclearly distinguish the brake pedal force signal from the accelerationsignal. In other words, even if the change in the acceleration of thevehicle and the change in the brake pedal force are related to eachother, the acceleration signal may not be used as it is because it isdifficult to distinguish the brake pedal effort signal from theacceleration signal. Therefore, a process confirming a change of theacceleration signal similar to the brake pedal force signal may berequired.

The controller 10 may extract a frequency of the brake of FIG. 6B fromthe acceleration signal of FIG. 6A by setting a certain frequency regionwhich is generated during the driver's brake operation and is shown inFIG. 5B, and may filter or block the remaining frequencies of theacceleration signal.

In general, during the brake operation, a high frequency region of theacceleration signal may represent a strong noise characteristic of thevehicle, and a low frequency region of the acceleration signal mayrepresent a strong characteristic of the vehicle's driving. Therefore,the controller 10 may set a band filter for the certain frequency region(i.e., the low frequency region) for discriminating the brake pedalforce signal from the acceleration signal in the braking operation.

The controller 10 may imitate the brake pedal force signal by extractingonly the certain frequency region of the brake through filtering of theacceleration signal collected during the brake operation. The imitatedbrake pedal force signal may include an overwhelmingly large signalchange component due to the brake operation. Thus, as shown in FIG. 4 ,the acceleration processing signal imitating the phase of the brakepedal force signal may be derived.

As described above, the controller 10 may obtain the accelerationprocessing signal reflecting a movement of the vehicle due to the brakeoperation by the filtering method that extracts the frequency region ofthe brake operation from the acceleration signal over time.

The controller 10 may store various programs and data for driving thebooster negative pressure predictor 100 and reducing a frequency of stopof the air conditioner using the booster negative pressure predictor ina memory, and may update data generated according to an operation of thecontroller.

The controller 10 may store a program of the booster negative pressurepredictor 100 in the memory, and may use a negative pressure of thebrake booster derived according to execution of the program to reducethe frequency of stop of the air conditioner.

The driving information detector 20 may detect driving informationrelated to the vehicle measured by various sensors and variouscontrollers according to a driving state of the vehicle. The drivinginformation may be data measured by various sensors and controllers, orinformation processed from measured raw data in a form necessary forcontrol.

For example, the driving information detector 20 may detect the drivinginformation from a vehicle speed sensor, a vehicle acceleration sensor,an intake manifold pressure sensor, a gear stage sensor, an acceleratorpedal sensor, a brake pedal sensor (or a brake pedal operation sensor),an altitude sensor, a slope sensor, a timer, or an atmospheric pressuresensor.

The air conditioning controller 30 may control an overall operation ofthe air conditioner (A/C), and may perform a control for reducing afrequency of stop of the air conditioner according to a signal appliedby the controller 10. The air conditioner may include a compressor thatcompresses refrigerant, a condenser that condenses and liquefies thecompressed refrigerant, and a vaporizer that vaporizes the liquefiedrefrigerant. The compressor, the condenser, and the vaporizer are knownelements.

FIG. 7 is a block diagram showing a configuration of the boosternegative pressure predictor according to various exemplary embodimentsof the present invention.

Referring to FIG. 7 , the booster negative pressure predictor 100 maycollect the negative pressure of the intake manifold and the drivinginformation in real time, and may generate the negative pressure k ofthe brake booster at a cycle of a predetermined time period.

The booster negative pressure predictor 100 may include a charging modelmodule 110 that determines the charging rate and a discharging modelmodule 120 that determines a discharging rate. The booster negativepressure predictor 100 may predict the negative pressure k of the brakebooster by integrating the change rate which is a sum of the chargingrate and the discharging rate.

The booster negative pressure predictor 100 may include the chargingmodel module (or a filling model module) 110, the discharging modelmodule 120, a summing module 130, and an integration module 140.

The charging model module 110 or the discharging model module 120 mayreceive the negative pressure k−1 of the brake booster determined in theprevious cycle, and the driving information including a negativepressure of the intake manifold, a brake operation signal, a brake pedalforce signal, the imitated brake pedal force signal imitating the changein the acceleration of the vehicle, speed of the vehicle, andacceleration of the vehicle of the current cycle.

The charging model module 110 may determine a first differentialpressure over time using the negative pressure k−1 of the brake boostermodeled (or determined) in the previous cycle and a current negativepressure of the intake manifold. The first differential pressure may beoutput as a positive value which is the charging rate (hPa/sec) of thebooster negative pressure. The charging model module 110 may determinethe charging rate (hPa/sec) of the booster negative pressure using apredetermined control map (or a predetermined control lookup table)using the first differential pressure as an input value thereof.

A difference between the current negative pressure of the intakemanifold and the negative pressure k−1 of the brake booster modeled oroutput in the previous cycle may be used as a main input factor. Thecharging model module 110 may determine the charging rate (hPa/sec) byreflecting additional correction factors referring to the drivinginformation.

The discharging model module 120 may take a difference between thenegative pressure k−1 of the brake booster modeled in the previous cycleand the current negative pressure of the intake manifold as a basicfactor, and may compensate for the basic factor using the imitated brakepedal force signal to determine a second differential pressure overtime. The second differential pressure may be output as a negative valuewhich is the discharging rate (hPa/sec) of the booster negativepressure. The brake pedal force signal may have the compensation valueproportional to its change. The discharging model module 120 maydetermine a multiplication factor for correcting the discharging rate ofthe booster negative pressure using a predetermined correction map usinga displacement change amount of the imitated brake pedal force as aninput value thereof.

The summing module 130 may determine the change rate by adding thedischarging rate of the second differential pressure determined in thedischarging model module 120 to the charging rate of the firstdifferential pressure determined in the charging model module 110.

The integration module 140 may integrate the change rate determined bythe summing module 130 over time to output the predicted negativepressure k of the brake booster.

The integration module 140 may feedback or transmit the predictednegative pressure of the brake booster to the charging model module 110and the discharging model module 120 so that the predicted negativepressure is used to determine a charging rate and a discharging rate ofa next cycle.

When repeated braking due to an on state and an off state of the brakeoperation signal (or a brake signal) continuously occurs, thedischarging model module 120 may reflect or use a predeterminedadditional correction amount to increase the discharging rate of thebooster negative pressure. In more details, the discharging model module120 may increase the discharging rate which is the negative value toforcibly reduce the negative pressure k of the brake booster when thedischarging model module detects the repeated braking according to acontinuous operation of the brake pedal shown as the condition {circlearound (3)} of FIG. 1 . Thus, the failure may be prevented.

A main factor of the forced reduction of the negative pressure may be arepetition frequency of the zero crossing according to the repeatedbraking of the brake. A reason for using the repetition of the zerocrossing to reduce the failure is that the repeated braking of the brakeis not reflected in the acceleration of the vehicle due to inertia ofthe vehicle when the pedal pressure is repeatedly generated at a highspeed. Therefore, the repeated braking of the brake may be reflected inthe acceleration of the vehicle by applying a predetermined additionalcorrection amount according to the repetition frequency of the zerocrossing.

The discharging model module 120 may reflect or use a predeterminedadditional correction amount to increase the discharging rate of thebooster negative pressure when the discharging model module continuouslydetects that the acceleration of the vehicle or a speed of the vehiclehas an amplitude greater than or equal to a reference amplitude. Controlstability of the negative pressure k of the brake booster determinedaccording to the change of the brake pedal force may be secured.

When the negative pressure k of the brake booster predicted by thebooster negative pressure predictor 100 is less than or equal to areference negative pressure of the control for stopping the operation ofthe air conditioner, the controller 10 may determine that the boosternegative pressure is insufficient to stop the operation of the airconditioner.

Based on the configuration of the above-described system for predictingthe negative pressure of the brake booster, a method for predicting thenegative pressure of the brake booster of the vehicle according tovarious exemplary embodiments of the present invention will bedescribed.

The controller 10 may be implemented as at least one processor thatoperates the booster negative pressure predictor 100 using a program.The program may perform each step of the method for predicting thenegative pressure of the brake booster of the vehicle according tovarious exemplary embodiments of the present invention.

Therefore, in the following description of the method for predicting thenegative pressure of the brake booster according to various exemplaryembodiments of the present invention, the subject or a main agent of themethod may be the controller 10, and the method may perform the controlfor reducing a frequency of stop of the air conditioner using thepredicted negative pressure k of the brake booster.

FIG. 8 is a flowchart showing the method for predicting the negativepressure of the brake booster of the vehicle according to variousexemplary embodiments of the present invention.

Referring to FIG. 8 , the controller 10 of the system for predicting thenegative pressure of the brake booster of the vehicle 1 may continuouslycollect the driving information related to the vehicle from the drivinginformation detector 20 after the vehicle is started (steps S1 and S2).The driving information may include at least one of the atmosphericpressure, the vehicle speed, the vehicle acceleration, an acceleratorpedal operation signal, the brake operation signal, an altitude, aslope, and a time according to an operation (or a driving) of thevehicle.

The controller 10 may generate the imitated brake pedal force signalimitating a change in acceleration of the vehicle over time in anoperation section of the brake (step S3). The controller 10 may generatethe imitated brake pedal force signal over time by filtering theacceleration change signal of the vehicle. The controller 10 maygenerate the acceleration inflection recognition signal by crossing theacceleration processing signal with the predetermined reference linewhich is 0 (or the zero crossing).

The controller 10 may determine the negative pressure of the intakemanifold by subtracting the pressure of the intake manifold from theatmospheric pressure which is the driving information (step S4).

The controller 10 may operate the timer so that the controller starts todetermine the negative pressure k of the brake booster using the drivinginformation, the imitated brake pedal force signal, and the negativepressure of the intake manifold collected in the current cycle and thenegative pressure k−1 of the brake booster determined in the previouscycle (step S5). The controller 10 may set an initial negative pressureof the brake booster generated when the previous cycle does not exist asa value less than the negative pressure of the intake manifold.

The controller 10 may determine the first differential pressure overtime using the negative pressure k−1 of the brake booster determined inthe previous cycle and the current negative pressure of the intakemanifold to determine the charging rate of the booster negative pressure(step S6).

The controller 10 may take the difference between the negative pressurek−1 of the brake booster determined in the previous cycle and thecurrent negative pressure of the intake manifold as the basic factor andmay compensate for the basic factor using the imitated brake pedal forcesignal to determine the second differential pressure over time so thatthe controller determines the discharging rate of the booster negativepressure (step S7). The controller 10 may determine the multiplicationfactor for correcting the discharging rate of the booster negativepressure using the correction map using the displacement change amountof the imitated brake pedal force as the input value.

The controller 10 may determine the change rate by adding thedischarging rate of the second differential pressure to the chargingrate of the first differential pressure (step S8).

The controller 10 may integrate the determined change rate over time togenerate the predicted negative pressure k of the brake booster (stepS9). The controller 10 may store the predicted negative pressure of thebrake booster in the memory so that the predicted negative pressure isused to determine a charging rate and a discharging rate of the nextcycle.

When the predicted negative pressure k of the brake booster is less thanor equal to the reference negative pressure of the control for stoppingthe operation of the air conditioner (Yes in step S10), the controller10 may determine that the booster negative pressure is insufficient tostop the operation of the air conditioner (step S11).

After the step S11, the controller 10 may return to the step S5 and maydetermine a negative pressure of the brake booster of the next cycleuntil the start of the vehicle is off.

When the predicted negative pressure k of the brake booster exceeds thereference negative pressure of the control for stopping the operation ofthe air conditioner (No in the step S10), the controller 10 maydetermine that the booster negative pressure is sufficient not to stopthe operation of the air conditioner, and may perform the step S5.

FIG. 9 is a graph showing a result of predicting the negative pressureof the brake booster according to various exemplary embodiments of thepresent invention.

FIG. 9 shows a control result using the system for predicting thenegative pressure of the brake booster according to various exemplaryembodiments of the present invention.

As described referring to FIG. 1 , when only the negative pressure ofthe intake manifold and the acceleration of the vehicle are used asbasic factors for prediction of the booster negative pressure, there isa problem that the predicted value is not similar to the measured valueso that the accuracy deteriorates or the failure occurs.

Accordingly, the exemplary embodiment of the present invention mayoutput the predicted value of the negative pressure of the brake boostersimilar to the measured value of the negative pressure of the brakebooster using the charging rate and the discharging rate generated basedon the imitated brake pedal force, and may improve the accuracy as muchas more than or equal to 90%.

As described above, the exemplary embodiment of the present inventionmay implement the logic for predicting the negative pressure of thebrake booster so that the exemplary embodiment of the present inventionimproves cooling performance and braking performance of the vehiclewithout cost increase due to addition of hardware.

The exemplary embodiment of the present invention may determine thenegative pressure of the brake booster based on the charging rate andthe discharging rate modeled according to a change of the imitated brakepedal force signal imitating a change in acceleration of the vehicle sothat the exemplary embodiment of the present invention improves accuracyof the negative pressure of the brake booster to a level similar to alevel of a measured value of the brake booster sensor.

Furthermore, the exemplary embodiment of the present invention mayforcibly reduce the predicted value of the negative pressure of thebrake booster by detecting the repeated braking situation in which thebrake pedal operation force signal is continuously changed and anacceleration signal of the vehicle is continuously changed more than orequal to the reference amplitude so that the exemplary embodiment of thepresent invention prevents the failure up to 0%.

The exemplary embodiment of the present invention has been described,but the present invention is not limited to the above describedexemplary embodiment of the present invention, and various othermodifications are possible.

For example, in the above described exemplary embodiment of the presentinvention, it has been described that the controller 10 performs thecontrol for reducing a frequency of stop of the air conditioner usingthe negative pressure of the brake booster predicted by the boosternegative pressure predictor 100.

However, the exemplary embodiment of the present invention is notlimited thereto, and the booster negative pressure predictor 100 mayinclude a function of a brake booster sensor of an existing vehicle.

In general, a vehicle including an idle stop and go (ISG) systemutilizes the brake booster sensor to restart the vehicle when a pressureof the brake booster becomes insufficient after start of the vehicle isstopped by the ISG system. Therefore, when the brake booster sensor isomitted in the vehicle including the ISG system, the vehicle may use thesystem for predicting the negative pressure of the brake booster of thevehicle 1 according to various exemplary embodiments of the presentinvention to perform ISG control.

For example, the controller 10 may restart the vehicle when thepredicted negative pressure of the brake booster of the step S9 is lessthan or equal to a reference negative pressure of the ISG control, andthe controller may maintain a state in which the start of the vehicle isstopped when the predicted negative pressure of the brake boosterexceeds the reference negative pressure.

The exemplary embodiment of the present invention is not implementedonly by the aforementioned apparatus or method, and may be implementedby a program for operating a function corresponding to the configurationof the exemplary embodiment of the present invention, a recording mediumin which the program is recorded, and the like, and the implementationmay be easily realized from the description of the aforementionedexemplary embodiment by those skilled in the art.

Furthermore, the term related to a control device such as “controller”,“control unit”, “control device” or “control module”, etc refers to ahardware device including a memory and a processor configured to executeone or more steps interpreted as an algorithm structure. The memorystores algorithm steps, and the processor executes the algorithm stepsto perform one or more processes of a method in accordance with variousexemplary embodiments of the present invention. The controller accordingto exemplary embodiments of the present invention may be implementedthrough a nonvolatile memory configured to store algorithms forcontrolling operation of various components of a vehicle or data aboutsoftware commands for executing the algorithms, and a processorconfigured to perform operation to be described above using the datastored in the memory. The memory and the processor may be individualchips. Alternatively, the memory and the processor may be integrated ina single chip. The processor may be implemented as one or moreprocessors.

The control device may be at least one microprocessor operated by apredetermined program which may include a series of commands forcarrying out the method included in the aforementioned various exemplaryembodiments of the present invention.

The aforementioned invention can also be embodied as computer readablecodes on a computer readable recording medium. The computer readablerecording medium is any data storage device that can store data whichmay be thereafter read by a computer system. Examples of the computerreadable recording medium include hard disk drive (HDD), solid statedisk (SSD), silicon disk drive (SDD), read-only memory (ROM),random-access memory (RAM), CD-ROMs, magnetic tapes, floppy discs,optical data storage devices, etc. and implementation as carrier waves(e.g., transmission over the Internet).

In an exemplary embodiment of the present invention, each operationdescribed above may be performed by a controller, and the controller maybe configured by a plurality of controllers, or an integrated singlecontroller.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”,“upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”,“inwardly”, “outwardly”, “interior”, “exterior”, “internal”, “external”,“inner”, “outer”, “forwards”, and “backwards” are used to describefeatures of the exemplary embodiments with reference to the positions ofsuch features as displayed in the figures. It will be further understoodthat the term “connect” or its derivatives refer both to direct andindirect connection.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described toexplain certain principles of the invention and their practicalapplication, to enable others skilled in the art to make and utilizevarious exemplary embodiments of the present invention, as well asvarious alternatives and modifications thereof. It is intended that thescope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A system for predicting a negative pressure of abrake booster of a vehicle, the system comprising: a driving informationdetector configured to detect driving information related to the vehicleaccording to driving of the vehicle; and a controller engaged to thedriving information detector and configured to determine a negativepressure of an intake manifold according to a pressure of the intakemanifold and an atmospheric pressure which is the driving information,wherein the controller includes a booster negative pressure predictorconfigured to predict the negative pressure of the brake booster byintegrating over time a change rate according to a charging rate and adischarging rate of the negative pressure of the brake boosterdetermined using a negative pressure of the brake booster determined ina previous cycle according to a logic for predicting the negativepressure of the brake booster and the negative pressure of the intakemanifold of a current cycle and an imitated brake pedal force signal ofthe current cycle imitating an acceleration of the vehicle and thecontroller is configured to control a restart of the vehicle accordingto the predicted negative pressure of the brake booster, wherein thebooster negative pressure predictor includes: a charging model moduleconfigured to determine a first differential pressure over time usingthe negative pressure of the brake booster determined in the previouscycle and the negative pressure of the intake manifold of the currentcycle; a discharging model module configured to take a differencebetween the negative pressure of the brake booster determined in theprevious cycle and the negative pressure of the intake manifold of thecurrent cycle as a basic factor, and to compensate for the basic factorusing the imitated brake pedal force signal to determine a seconddifferential pressure over time; a summing module configured todetermine the change rate by adding a discharging rate of the negativepressure of the brake booster corresponding to the second differentialpressure to the charging rate of the negative pressure of the brakebooster corresponding to the first differential pressure; and anintegration module configured to integrate the change rate over time andto output the predicted negative pressure of the brake booster.
 2. Thesystem of claim 1, wherein the controller is configured to generate anacceleration inflection recognition signal by crossing the imitatedbrake pedal force signal over time and a reference line which is a zerocrossing.
 3. The system of claim 2, wherein the controller is configuredto correct the charging rate and the discharging rate according to theacceleration inflection recognition signal.
 4. The system of claim 1,wherein when a predicted negative pressure of the brake booster is lessthan or equal to a reference negative pressure of a control for stoppingan operation of an air conditioner of the vehicle, the controller isconfigured to stop the operation of the air conditioner.
 5. The systemof claim 1, wherein the driving information detector is configured todetect the driving information from at least one of a vehicle speedsensor, a vehicle acceleration sensor, a gear stage sensor, anaccelerator pedal sensor, a brake pedal operation sensor, a timer, andan atmospheric pressure sensor.
 6. The system of claim 1, wherein thebooster negative pressure predictor is configured to collect thenegative pressure of the intake manifold and the driving information andto generate the negative pressure of the brake booster predicted in acycle of a time period.
 7. The system of claim 1, wherein the chargingrate of the negative pressure of the brake booster according to thefirst differential pressure is output as a positive value, and thedischarging rate of the negative pressure of the brake booster accordingto the second differential pressure is output as a negative value. 8.The system of claim 1, wherein the charging model module is configuredto determine the charging rate using a control map using the firstdifferential pressure as an input value thereof.
 9. The system of claim1, wherein the discharging model module is configured to determine amultiplication factor for correcting the discharging rate using acorrection map using a displacement change amount of the imitated brakepedal force as an input value thereof.
 10. The system of claim 9,wherein the discharging model module is configured to use an additionalcorrection amount according to a repetition frequency of a zero crossinggenerated upon determining that repeated braking due to an on state andan off state of a brake operation signal continuously occurs to increasethe discharging rate.
 11. The system of claim 10, wherein thedischarging model module is configured to use an additional correctionamount to increase the discharging rate upon determining that thedischarging model module continuously detects that the acceleration ofthe vehicle or a speed of the vehicle has an amplitude greater than orequal to a reference amplitude.
 12. The system of claim 1, wherein theintegration module is configured to feedback the predicted negativepressure of the brake booster to the charging model module and thedischarging model module so that the predicted negative pressure is usedto determine a charging rate and a discharging rate of a next cyclegenerated after the current cycle.
 13. The system of claim 1, whereinthe controller is configured to restart the vehicle in a state in whicha start of the vehicle is stopped by an idle stop and go (ISG) systemupon determining that the predicted negative pressure of the brakebooster is less than or equal to a reference negative pressure.
 14. Amethod for predicting a negative pressure of a brake booster of avehicle, the method comprising: a) collecting, by a controller, drivinginformation related to the vehicle according to driving of the vehicleto determine an imitated brake pedal force signal imitating change of anacceleration of the vehicle and a negative pressure of an intakemanifold; b) determining, by the controller, a first differentialpressure over time using a negative pressure of the brake boosterdetermined in a previous cycle and the negative pressure of the intakemanifold of a current cycle; c) taking, by the controller, a differencebetween the negative pressure of the brake booster determined in theprevious cycle and the negative pressure of the intake manifold of thecurrent cycle as a basic factor to determine a second differentialpressure over time and compensating the imitated brake pedal forcesignal to the basic factor; and d) determining, by the controller, achange rate by adding a discharging rate of the negative pressure of thebrake booster corresponding to the second differential pressure to acharging rate of the negative pressure of the brake boostercorresponding to the first differential pressure to predict the negativepressure of the brake booster by integrating the change rate over time,wherein the controller is configured to control a restart of the vehicleaccording to the predicted negative pressure of the brake booster. 15.The method of claim 14, wherein step a) includes: generating, by thecontroller, the imitated brake pedal force signal over time by filteringan acceleration change signal of the vehicle in an operation section ofa brake of the vehicle; and generating, by the controller, anacceleration inflection recognition signal by crossing the imitatedbrake pedal force signal and a reference line which is a zero crossing.16. The method of claim 14, wherein step b) includes: setting, by thecontroller, an initial negative pressure of the brake booster generatedupon determining that the previous cycle does not exist as a value lessthan the negative pressure of the intake manifold.
 17. The method ofclaim 14, wherein step b) includes: determining, by the controller, thecharging rate using a control map using the first differential pressureas an input value thereof.
 18. The method of claim 14, wherein step c)includes: determining, by the controller, a multiplication factor forcorrecting the discharging rate using a correction map using adisplacement change amount of the imitated brake pedal force as an inputvalue thereof.
 19. The method of claim 14, further including: after stepd), restarting, by the controller, the vehicle in a state in which astart of the vehicle is stopped by an idle stop and go (ISG) system upondetermining that the predicted negative pressure of the brake booster isless than or equal to a reference negative pressure.